Method of forming stretchable encapsulation for electronic displays

ABSTRACT

A method of encapsulating an organic light-emitting diode display includes depositing a plurality of first polymer projections onto a light-emitting side of a display layer having a plurality of organic light-emitting diodes (OLEDs) such that the plurality of first polymer projections have spaces therebetween that expose an underlying surface, and conformally coating the first polymer projections and the spaces between the first polymer projections with a first dielectric layer such that the first dielectric layer has side walls along sides of the first polymer projections and defines wells in spaces between the side walls.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of and claims priority toU.S. application Ser. No. 16/698,835, filed on Nov. 27, 2019, thedisclosure of which is incorporated by reference.

TECHNICAL FIELD

This disclosure relates to electronic displays, and more particularly toencapsulation layers for protecting components, particularly organiclight emitting diodes, in an electronic display.

BACKGROUND

An electronic display typically includes multiple layers deposited on asubstrate. For example, an organic light-emitting diode (OLED) displayincludes, on a substrate, a back-plane (e.g., one that includeselectrical control elements such as thin film transistors), afront-plane, an encapsulation, and other functional elements (e.g.,touch-sensitive components, a hard coat, a polarizer) in variousconfigurations (in-cell, on-cell). The front-plane includes an anodelayer, a conductive layer, an emissive layer, and a cathode layer. Atypical OLED display can also include an encapsulation to protect thelayers of the display, e.g., from ambient oxidants (e.g., moisture,oxygen), dust, and other atmospheric conditions. Typically, theencapsulation is provided by a glass lid or by one or more barrierlayers. For a flexible encapsulation, the OLED display can be coated bya barrier bi-layer that includes a stack of two generally planar andcontinuous layers: an organic layer and an inorganic layer.

SUMMARY

In one aspect, a display device includes a display layer having aplurality of organic light-emitting diodes (OLEDs) and an encapsulationlayer covering a light-emitting side of the display layer. Theencapsulation layer includes a plurality of first polymer projections ondisplay layer, the plurality of first polymer projections having spacestherebetween, and a first dielectric layer conformally covering theplurality of first polymer projections and any exposed underlyingsurface in the spaces between the first polymer projections, thedielectric layer forming side walls along sides of the first polymerprojections and defining wells in spaces between the side walls.

In another aspect, the spaces between the first polymer projectionsexpose an underlying surface.

In another aspect, the plurality of first polymer projections are aplurality of curved convex polymer projections on the underlyingdielectric layer.

In another aspect, the plurality of first polymer projections have sidesthat are substantially perpendicular to the top surface of the displaylayer and an upper surface that is substantially parallel to the topsurface.

In another aspect, a plurality of second polymer projections aredisposed on the first dielectric layer, the plurality of second polymerprojections having spaces therebetween that expose the first dielectriclayer, and a second dielectric layer conformally covers the plurality ofsecond polymer projections and the first dielectric layer in the spacesbetween the plurality of second polymer projections, the seconddielectric layer forming side walls along sides of the plurality ofsecond polymer projections and defining wells in spaces between the sidewalls of the second dielectric layer.

In another aspect, the encapsulation layer includes a plurality ofbilayers, each bilayer including a plurality of polymer projections anda dielectric layer.

In another aspect, the side walls are aligned with the gaps between theOLEDS.

In another aspect, the side walls are positioned at a uniform lateralpositions relative the OLEDs, to pixels comprising a plurality of OLEDs,or to groups of pixels.

In another aspect, a method of encapsulating an organic light-emittingdiode display includes depositing a plurality of first polymerprojections onto a light-emitting side of a display layer having aplurality of organic light-emitting diodes (OLEDs) such that theplurality of first polymer projections have spaces therebetween thatexpose an underlying surface, and conformally coating the first polymerprojections and the spaces between the first polymer projections with afirst dielectric layer such that the first dielectric layer has sidewalls along sides of the first polymer projections and defines wells inspaces between the side walls.

Implementations may include one or more of the following features.

The display layer may have a capping layer covering the plurality oforganic light-emitting diodes. The display layer may have a non-planartop surface. The underlying surface may be a top surface of the displaylayer.

The encapsulation layer may include an underlying dielectric layercontacting and conformally covering the display layer, and theunderlying surface may be a top surface of the underlying dielectriclayer. The underlying dielectric layer may be the same material as thefirst dielectric layer.

The first dielectric layer may be an inorganic oxide or mixture ofinorganic oxides. The first polymer projections may be a photoresist.

The plurality of first polymer projections may be provided by aplurality of discrete projections. At least a portion of the sides of atleast one first polymer projection may be at an oblique angle relativeto the underlying surface. The first polymer projections may be curvedconvex projections, e.g., hemispherical projections. The sides of atleast one first polymer projection may be at right angles relative tothe underlying surface. The plurality of first polymer projections mayinclude a plurality of annular projections having one or more sidewalls, and spaces between the polymer projections may include anaperture surrounded by the one or more side walls of the annularprojections. The plurality of annular projections may be hexagonal.

The plurality of first polymer projections may be provided by aninterconnected structure having a plurality of apertures, and whereinthe spaces between the first polymer projections may be provided by theplurality of apertures. The interconnected structure may be ahoneycomb-shaped structure.

A polymer filler may partially or completely fill the wells. The polymerfiller may cover the first dielectric layer.

The first polymer projections and the second polymer projections may bethe same polymer material, and the first dielectric material and seconddielectric material may be the same dielectric material.

The second dielectric layer may contact the first dielectric layer. Thesecond dielectric layer may contact the first dielectric layer inregions between the sides of adjacent polymer projections. The seconddielectric layer may be separated from the first dielectric layer by apolymer in regions over the first plurality of polymer projections.

The second polymer projections may be aligned above the first polymerprojections. The second polymer projections may be laterally offset fromthe first polymer projections. The first polymer projections may behexagonal close packed and the second polymer projections may behexagonal close packed and offset relative to the first plurality ofpolymer projections.

A plurality of third polymer projections may be disposed on the seconddielectric layer. The third polymer projections may have spacestherebetween that expose the second dielectric layer. A third dielectriclayer may conformally cover the third polymer projections and the seconddielectric layer in the spaces between the third polymer projections.The third dielectric layer may form side walls along sides of the thirdpolymer projections and defining wells in spaces between the side wallsof the third dielectric layer. A polymer filler may completely fill thewells in the spaces between the side walls of the second dielectriclayer. The polymer filler may cover the third dielectric layer.

A polymer filler layer may cover the dielectric layer of an outermost ofthe plurality of bilayers.

At least two of the polymer projections may span a plurality of OLEDs.The plurality of organic light-emitting diodes (OLEDs) may include OLEDtuples of different colors, and wherein at least two of the polymerprojections may span OLED tuples. The plurality of organiclight-emitting diodes may include a plurality of pixels, each pixelincluding an OLEDs tuple of different colors, and the side walls may bealigned with gaps between the pixels. The pixels may be arranged in astripe pixel geometry or a PenTile pixel geometry. At least two of thepolymer projections may span a plurality of pixels.

An underlying dielectric layer may be deposited to contact andconformally cover the display layer, and the first polymer projectionsmay be deposited on the underlying dielectric layer.

Depositing the plurality of first polymer projections may includedroplet ejection of a liquid polymer precursor onto the underlyingsurface. The liquid polymer precursor may be cured form the firstpolymer projections. The droplet ejection may include ejecting asequence of droplets, and each droplet may form a single projection fromthe plurality of first polymer projections. The droplet may form acurved convex projection on the underlying surface.

Depositing the plurality of polymer projections may includemicro-imprint or nano-imprint lithography.

The subject matter described in this specification can be implemented toprovide, but is not limited to, one or more of the following advantages.Electronic displays, e.g., OLED displays, can be protected by anencapsulation that features increased durability compared toconventional encapsulations. The electronic device can be bent, flexed,or stretched with reduced risk of damage or failure. The encapsulationcan be fabricated at a commercially viable cost.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features, aspects, andadvantages will become apparent from the description, the drawings, andthe claims.

DESCRIPTION OF DRAWINGS

FIG. 1A is a schematic diagram of the layers in an OLED device.

FIG. 1B is a schematic diagram of an OLED display with multiple OLEDsand that includes a subpixel defining layer with apertures that extendthrough the layer and OLEDs in the apertures.

FIG. 2A is a schematic cross-sectional view of an OLED device thatincludes a subpixel defining layer.

FIG. 2B is a schematic cross-sectional view of an OLED device.

FIG. 3A illustrates a cross-sectional view of an initial conformalcoating on a front-plane of an OLED device, with an initial polymerlayer being deposited on the conformal coating.

FIG. 3B illustrates a cross-sectional view of the device of FIG. 3A witha first encapsulation sublayer formed on the initial conformal coating.

FIG. 3C illustrates a cross-sectional view of the device of FIG. 3A witha first encapsulation sublayer formed on the initial conformal coating.

FIG. 3D illustrates a cross-sectional view of the device of FIG. 3B witha second encapsulation sublayer formed on the first encapsulationsublayer.

FIG. 4 illustrates a thermal NIL process and UV NIL process fordepositing features on a substrate.

FIGS. 5A and 5B illustrate a top view of the flexible polymer layers ofFIG. 2C.

FIG. 6A illustrates a perspective view of a polymer subunit that can bedeposited on top of the front-plane of a OLED display.

FIG. 6B illustrates a perspective view of the polymer subunit of FIG. 6Acoated by a conformal coating to form an encapsulation cell.

FIG. 6C illustrates a perspective view of multiple encapsulation cellspositioned next to one another to form a first encapsulation sublayer.

FIG. 7A illustrates a cross-sectional view of the front-plane andsubstrate as covered by the first encapsulation sublayer of FIG. 6C.

FIG. 7B illustrates a cross-sectional view of the front-plane andsubstrate as covered by an encapsulation that includes threeencapsulation sublayers in an aligned configuration.

FIG. 7C illustrates a cross-sectional view of the front-plane andsubstrate as covered by an encapsulation that includes threeencapsulations sublayers in an unaligned configuration.

FIG. 8 illustrates a top view of an encapsulation layer that includeshexagonal polymer subunits.

FIG. 9A illustrates an example stripe pixel geometry for an OLED device.

FIG. 9B is a schematic cross-sectional view of a portion of the stripepixel geometry of FIG. 9A.

FIG. 10 illustrates an example PenTile pixel geometry for an OLEDdevice.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

A stretchable, flexible electronic display is desirable for some displayapplications, e.g., television displays or mobile phone displays.However, conventional stretchable displays, and techniques for makingthem, are prone to a number of problems. Many conventional stretchabledisplays include inorganic materials that are brittle and vulnerable tocracking when the display is bent or stretched. For example, inorganicmaterials can be found in the encapsulation layer and in othersubcomponents of the electronic display (e.g., a back-plane of thedisplay that includes electronic circuitry, e.g., thin-film transistors(TFTs), to drive the light emitting elements).

Bending or stretching a conventional display can result in adistribution of stress that varies between the layers along the depth ofthe display. For example, bending a display subjects one face of thedisplay to compressive stress and the opposite face to tensile stress.Thus, a region between the two faces of the display may bestress-neutral as the stress distribution transitions from compressiveto tensile stress through the depth of the display. A conventionalapproach to stretchable displays is to attempt to position layers of thedisplay in a “stress-neutral” plane. However, the finite thickness ofcertain display elements, e.g., the back-plane, frontplane, andthin-film encapsulation (TFE), can result in critical layers beingpositioned outside the stress-neutral plane. As a result, these layersare subjected to failures.

The subject matter described herein pertains to a thin-filmencapsulation that is more robust during bending, flexing, andstretching. Unlike conventional stretchable displays, the displaysdescribed herein can include a back-plane and front-plane that are inthe stress-neutral plane, while the TFE can be positioned outside of thestress-neutral plane, thus making the display more robust.

Cracks in the encapsulation layer permit moisture and other oxidants toreach the light emitting layer, reducing display lifetime or introducingvisual defects. Moreover, the cracks in the encapsulation layer canthemselves cause visual defects, e.g., black spots or aberrant lightpaths on the display, decreasing picture quality.

Encapsulation techniques discussed herein can provide increasedflexibility and stretchability for electronic displays, as well asincreased durability for flexible and/or stretchable electronicdisplays. One such technique includes layers of polymer dotsinterspersed with conformal dielectric layers. Another techniqueincludes one or more polymer lattices interspersed with conformaldielectric layers. Such structures should be highly flexible andstretchable without incurring significant damage to the encapsulation.Without being limited to any particular theory, when the device isstretched horizontally, vertically extending portions of the conformalbarrier layer can splay outward while the polymer material iscompressed. This permits the otherwise brittle barrier layer to bend orstretch with a reduced risk of cracking or incurring other defects. Forexample, the layer of polymer dots or lattices can conform to the shapethat the display is bent or stretched into, while the total length (inthis case including vertical excursions) of the conformal dielectriclayers remain roughly constant.

The encapsulation layers can be formed by sequential deposition oflayers of materials, for example, using an inkjet printer for thepolymer material. The polymer material of the encapsulation layer canalso be deposited using a nano- or micro-imprint lithography (NIL orMIL) process, e.g., a thermal NIL/MIL or UV NIL/MIL process. Theconformal barrier layer can be deposited by a vapor phase deposition,e.g., physical vapor deposition, chemical vapor deposition, or atomiclayer deposition.

FIGS. 1A and 1B illustrate schematic cross-sectional views of an OLEDdevice 100 and an OLED display 100′ that includes multiple OLED devices100. The OLED device 100 and OLED display 100′ include an encapsulation102 disposed over a front-plane 110. A Cartesian coordinate system isprovided for ease of reference. The OLED device 100 and OLED display100′ include a substrate 112 on which is formed a back-plane 113 thatprovides electronic circuitry, e.g., an array of thin-film transistors(TFTs), to drive the light-emitting elements of the front-plane 110.

The substrate 112 provides support to the other components of thefront-plane 110. That is, the substrate 112 can be a base layer on topof which the other components of the OLED device 100 are sequentiallydeposited during manufacturing. For example, the substrate 112 can beplastic or glass.

In some implementations, a sacrificial substrate is used duringmanufacturing to provide support for some portion of the front-plane,e.g., the front-plane 110 and encapsulation 102, but the substrate isremoved for the final device. For example, the back-plane 113,front-plane 110, and encapsulation 102 could be removed from a plasticor glass substrate, and optionally placed on a substrate, such as aflexible polymer layer, that is sufficiently flexible for the end usedevice, e.g., in a flexible display. In short, the substrate 112 that isused for the fabrication of the OLED devices can be less flexible thanthe substrate onto which the OLED devices are transported to build theend use device. Alternatively, the substrate 112 could sufficientlyflexible for the end use.

The front-plane 110 includes a lower conductive layer 114 a that canserve as an anode, an organic layer stack 116 that includes an emissivelayer 126, and an upper conductive layer 114 b that can serve as acathode. As an anode, the lower conductive layer 114 a is a patternedlayer that during operation provides a positively charged electricalcontact to the organic layer stack 116. The lower conductive layer 114 acan optionally be a reflective material, e.g., a stack of materials suchas a metal and indium tin oxide (ITO), with the metal being a conductivemetal such as Ag or an alloy containing Ag and another metal such as Mg.The upper conductive layer 114 b is transparent to allow thetransmission of light generated by the front-plane 110. The upperconductive layer 114 b can be, for example, ITO or a thin layer of ametal or alloy such as Ag or an alloy containing Ag and another metalsuch as Mg. In some implementations, the AgMg alloy can have a ratio ofapproximately 9:1 Ag to Mg.

A subpixel defining layer 115 can be deposited on the lower conductivelayer 114 a. The subpixel defining layer 115 can be formed of adielectric material, e.g., a polymer such as a photoresist material. Theapertures extend through the subpixel defining layer 115, and providewells in which the OLED devices are formed. In particular, the organiclayer stack 116 can be deposited over the bottom surface of the well.For example, the organic layer stack 116 can be disposed in spacesformed by the apertures e.g., using a fine metal mask (FMM). The lowerconductive layer 114 a is patterned to provide individual control of theOLED devices. The aperture permits the organic layer stack 116 tocontact the lower conductive layer 114 a or drive electrodes of theback-plane 113.

FIG. 2A illustrates a portion of an OLED display 100A′ that includes asubpixel defining layer 115 with apertures that define wells for theindividual OLED devices 100A. The wells can have oblique side walls, anda mirror layer can be formed at the bottom of the well and partially orentirely along the side wall of the well. The mirror layer can be addedto enhance the outcoupling of light from the OLED devices 100A. While insome embodiments, the anode of the OLED device is positioned at thebottom of the well formed between the subpixel defining layer, andextends underneath the subpixel defining layer without connecting to theanodes of adjacent subpixels. In other embodiments, an additional anodelayer is patterned on top of the anode layer that extends underneath thesubpixel defining layer.

The lower conductive layer 114 a is deposited at least at the bottom ofthe well to contact the drive electrodes of the back plane 113. Toprovide the mirror, the lower conductive layer 114 a can be a reflectivelayer, or the lower conductive layer 114 a can be coated with areflective layer, or the lower conductive layer 114 a can be atransparent conductive layer formed over a reflective layer. The lowerconductive layer can also be deposited on some or all of the sidewallsprovided by the apertures in the subpixel defining layer 115. As notedabove, the lower conductive layer 114 a is a patterned layer intodiscrete anodes that provide independent control of individual OLEDdevices 100A.

The organic layer stack 116 can be deposited over the lower conductivelayer 114 a and the portion of the subpixel defining layer that is notcovered by the lower conductive layer 114 a, e.g., on the side walls andtop of the plateaus between the wells provided by the subpixel defininglayer 115. Some layers of the organic layer stack 116 can span multipleOLED devices. The upper conductive layer 114 b is deposited over theorganic layer stack 116, and can be deposited as a continuous layer thatspans multiple OLED devices. Disposed over the upper conductive layer114 b and at least partially filling each well is a light enhancinglayer 120, e.g., an index matching material to improve the emission oflight.

Portions of the organic layer stack 116 in the apertures over theindividual anodes of the lower conductive layer 114 a thus provide thepixels or subpixels of the OLED display 100A′. That is, in someimplementations, each OLED device 100A can provide a particular color oflight, e.g., red, green or blue. FIG. 2B illustrates a portion of anOLED display 100B′ in which the OLED devices 100B are formed directly ona backplane 113. Various electrically insulating layers (notillustrated) can be used to prevent shorting between the common cathodeand other layers, e.g., the anode or metallization on the backplane 110.In some implementations, the OLED devices are formed without use of asubpixel defining layer 115. Although FIG. 2B illustrates the organiclayer stack 116 and upper conductive layer 114 b patterned with the samedimensions as the lower conductive layer 114 a, this is not necessary.Disposed over the upper conductive layer 114 b and remaining portion ofthe backplane 113 is a capping layer 117. Like the upper conductivelayer 114 b, the capping layer 117 can be deposited as a continuouslayer that spans multiple OLED devices.

Returning to FIG. 1A, the organic layer stack 116 can include anelectron injection layer (EIL) 120, an electron transport layer (ETL)122, a hole blocking layer (HBL) 124, the light emissive layer (EML)126, an electron blocking layer (EBL) 128, a hole transport layer (HTL)130, and a hole injection layer (HIL) 132. Light is generated in the EML126, e.g., through the recombination of positively charged holes, whichtravel to the EML from the lower conductive layer 114 a, and negativelycharged electrons, which travel to the EML from the upper conductivelayer 114 b.

The organic layer stack 116 is just one example of a multilayered stackof organic materials that can be used in a front-plane. In someimplementations, an organic layer stack for a front-plane can includefewer layers than those included in organic layer stack 116, or morelayers than those included in the organic layer stack. For example, oneor more additional layers, an organic layer stack can include more thanone HTLs, more than one HBLs, more than one EBLs, and/or more than oneETLs.

The organic layer stack 116, including the EML 126, can each be formedfrom a suitable organic material. For example, the organic material forthe EML 126 can include light-emitting polymers, e.g., polyphenylenevinylene or polyfluorene. The organic material can include moleculesthat are smaller than light-emitting polymers, e.g., Alq₃. The EML 126can also include quantum dots or other light-emissive materials.

A capping layer 117, which can be an organic layer, can be deposited onthe upper conductive layer 114 b (as shown in FIG. 2A), or over theupper conductive layer 114 b and exposed portions of the organic layerstructure and/or backplane 113 (as shown in FIG. 2B). In someembodiments, the capping layer 117 is a dielectric layer, while in otherembodiments the capping layer is formed from one or more organicsemiconductor materials. The capping layer 117 can form the top layer ofthe front-plane 110. In some implementations, the capping layer 117 canserve as a planarization layer. In some implementations, the cappinglayer 117 can serve as a light-enhancement layer, e.g., one thatperforms index matching to improve outcoupling of light from the OLEDs.In some implementations, the capping layer 117 can partially fillapertures formed by the subpixel defining layer 115 (see FIG. 2A). Insome implementations, the capping layer 117 can partially or entirelyfill gaps between the OLEDs, e.g., partially or partially fills inspaces between the organic layer stack 116, the lower conductive layer114 a, and the upper conductive layer 114 b or adjacent OLEDs (see FIG.2B).

The encapsulation 102 can be formed over the capping layer 117. Theencapsulation 102 can include multiple layers of materials successivelydeposited on top of one another. For example, the encapsulation 102 caninclude multiple encapsulation sublayers. At least some of theencapsulation sublayers can be bilayers (sometimes referred to as dyads)that include a polymer layer, e.g., of polymer dots, and a conformalcoating that acts as a barrier layer formed over the polymer layer. Forexample, the encapsulation can include two or more bilayers, followed bya conformal inorganic dielectric coating.

The conformal coating can be a dielectric material, e.g., an inorganicmaterial, such as SiO₂, SiOxNy, or Al₂O₃. The conformal coating can bedeposited using any method suitable for depositing conformal thin-filmlayers of materials, e.g., using a chemical vapor deposition (ALD, CVD,PECVD, etc.) process or a physical vapor deposition (PVD) process. Thethickness of the dielectric layer is approximately 1 μm or less (e.g.,0.8 μm or less, 0.6 μm or less, 0.4 μm or less, 0.2 μm or less, 0.1 μmor less, 0.05 μm or less, 0.02 μm or more, 0.05 μm or more). Forexample, the thickness can be 0.05 to 1 μm for a layer deposited by CVD,or 20 to 50 nm for a layer deposited by ALD.

The polymer layer can be formed of a liquid photopolymer adhesive, e.g.,Norland Optical Adhesive 63 (NOA63), of polycarbonate (PC),polyphenylene sulfide (PPS), polyetherimide (PEI), polyethersulfone(PES), polyethylene terephthalate (PET), polydimethylsiloxane (PDMS),polymide (PI), or silicone, of a photoresist, e.g., KMPR photoresist, orof a polystyrene (PS) array, such as PS with xylene or Parylene, such asParylene C, D, or N.

In particular, following the capping layer 117 can be an optionalinitial conformal coating 102 a of an inorganic dielectric material. Forexample, referring to FIG. 2B, an initial conformal coating 212 isdeposited on the capping layer 117.

On the initial conformal coating 102 a (see FIG. 1B), or on the cappinglayer 117 (see FIG. 2A), is an encapsulation sublayer (sometimes calleda first dyad) that is a bilayer that includes a first polymer layer 102b, e.g., of polymer dots, and a first conformal coating 102 c depositedon the first polymer layer 102 b. In some implementations, the firstpolymer layer 102 a can function both as a planarization layer, tocreate a layer that fills in any gaps formed by the subpixels of thefront-plane 110. Additional layers of conformal coatings and polymer canbe added on top of the first encapsulation sublayer.

In some embodiments, planarization of the wells formed between thesubpixel defining layer 115 can be performed by depositing a polymerlayer such that the polymer layer fills in the wells without the polymerlayer overflowing beyond the wells. For example, in such an embodiment,the polymer planarization layer can be deposited such that this layer issubstantially coplanar with the portions of the upper conductive layer114 b that are parallel to the xy-plane.

In other embodiments, the polymer planarization layer can overflowbeyond the wells formed between the subpixel defining layer 115, suchthat portions of the polymer planarization layer extend or bulge abovethe portions of the upper conductive layer 114 b that are parallel tothe xy-plane. In such embodiments, subsequent layers, e.g., conformalcoatings and/or additional polymer layers, can perform planarizationover the bulges formed by the polymer planarization layer.

For example, a second encapsulation sublayer that is a bilayer includinga second polymer layer 102 d, e.g., of polymer dots, and secondconformal coating 102 e, e.g., of an inorganic dielectric material, canbe deposited on top of the first encapsulation sublayer. Similarly, athird encapsulation sublayer that is a bilayer including third polymerlayer, e.g., of polymer dots, and a third conformal coating, e.g., of aninorganic dielectric material, can be deposited on top of the secondencapsulation sublayer, etc.

Referring to FIGS. 2A and 2B, a first encapsulation sublayer 210 isdeposited on the initial conformal coating 212 (see FIG. 2B), or on thecapping layer 117 (see FIG. 2A). The first encapsulation sublayerincludes a first polymer layer 214 and a first conformal coating 216deposited on the first polymer layer 214. Fabrication of this structureis described in greater detail below, with respect to FIGS. 3A-3D.

Returning to FIG. 1A, optionally, additional functional elements 111,e.g., polarization films, touch-sensitive components, a hard coating,etc., can be deposited on the encapsulation 102. In someimplementations, one of more of the conformal coatings conformal coatingcan serve as a hard coating, allowing for the omission of a hard coatingas part of the functional elements 111.

Although the layers of the encapsulation 102 are illustrated in FIG. 1Aas continuous planar layers, as explained below, at least some of thepolymer layers are patterned. As a result, at least some of theconformal layers, i.e., those conformal layers disposed over thepatterned polymer layer, have vertically extending portions. Withoutbeing limited to any particular theory, when the device is stretched,the vertically extending portions of the conformal layer can by splayoutward while the polymer material is compressed.

Referring to FIG. 3A, in manufacturing of the OLED display, e.g., thedisplay 100 of FIG. 1B, the encapsulation 102 is deposited on thefront-plane 110.

FIG. 3A illustrates a cross-sectional view of the front-plane 110 withan initial conformal coating 212 deposited on the front-plane and afirst polymer layer 214 deposited on the initial conformal coating. Thesubstrate 112 and back-plane 113 are omitted from FIG. 3A forsimplicity.

The conformal coating 212 can be a layer of dielectric material that isdeposited on top of the front-plate 110, e.g., deposited on top of thecapping layer 117 of the front-plane. The first conformal coating 212extends in the x and y-directions and can be deposited using a chemicalvapor deposition process (e.g., CVD, PECVD, ALD) or a physical vapordeposition process (PVD).

The first polymer layer 214, enclosed by broken lines, extends in the xand y-directions in a layer that sits on top of the initial conformalcoating 212. The first polymer layer 214 can include polymer dots 214 a.Because previous layers of the OLED display 100 can provideplanarization, e.g., a light enhancement layer, other polymerplanarization layer, or other layer of the light light-emitting elementsof the front-plane 110, the polymer dots 214 a form a plane that extendsin the x and y-directions.

As shown in FIG. 3A, the polymer dots 214 a can be substantiallysemispherical, although other shapes are possible, e.g., trapezoidal orrectangular. The flat face of each polymer dot 214 a is in contact withthe initial conformal coating 212. Alternatively, in someimplementations the flat face of each polymer dot 214 a is in contactwith the front-plane 110.

The first polymer layer 214 with the polymer dots 214 a can extendacross the surface of the front-plane 110, e.g., such that an array ofpolymer dots is deposited on the top surface of the structure, extendingin the x and y-directions. Adjacent polymer dots 214 a are spaced apartby a gap. As such, the polymer dots 214 a do not contact one another.The polymer dots can be distributed with uniform spacing at least acrossthe regions of the front-plane 110 that will provide the display, e.g.,across the entire workpiece. The polymer dots 214 a can be distributedin a hexagonal pattern, although other patterns, such as rectangularpatterns, are possible.

The polymer dots 214 a can be deposited by a droplet ejection printer240, similar to an inkjet printer, which is coupled to a controller 242.In particular, droplets 244 can be controllably ejected from one or morenozzles onto the initial conformal coating 212 in a desired pattern. Thedroplet can then be cured, e.g., by UV radiation from a UV light source.An advantage of droplet ejection printing is that a printhead caninclude multiple nozzles in one or more rows that span a width of theworkpiece, and the printhead can be driven along the length of theworkpiece while droplets are controllably ejected. This permits quickfabrication of the polymer layer 214.

Alternatively, the polymer layer 214 can be deposited by other suitableprocesses, e.g., a nano- or micro-imprint lithography (NIL or MIL)process that deposits the polymer features. The described processes mayinvolve multiple imprinting, e.g., to form a repeated structure offeatures, and control over the alignment of features, e.g., to ensure aconsistent spacing of features relative to each other. Referring to FIG.4, in both of these NIL/MIL processes, a substrate 412, i.e., thesubstrate 112 with the front-plane 110 and back-plane 113 thereon, iscoated with a resist 402, e.g., a thermoplastic polymer resist orphotopolymer resist, depending on the type of process. A mold or mask404 is applied to the resist 402 and the mold and resist are thenexposed to heat (for thermal NIL/MIL), or ultraviolet light (for UVNIL/MIL). In some implementations, for thermal NIL/MIL processes, thetemperature at which the resist 402 and mask 404 are heated can be abovethe glass transition temperature of the photoresist. In someimplementations, for thermal NIL/MIL processes, the temperature canrange from about 80° C. to about 100° C. For UV NIL/MIL processes, theresist 402 and mask 404 can be exposed to UV light while at roomtemperature. In other implementations, the temperature range for UVNIL/MIL processes can be about 80° C. to about 100° C. Exposing theresist 402 to heat or light causes the resist to be cured and set. Whenthe mold 404 is removed, the top surface of the resist 402 bears anegative imprint of the mold. The resist 402 thus provides the polymerlayer 214.

NIL/MIL can provide certain advantages over other processes, e.g., thosethat include a droplet injection printer. For example, NIL/MIL processescan be faster than other feature deposition processes. As anotheradvantage, NIL/MIL processes can create a greater range of patternscompared to other processes. For example, NIL/MIL processes can enablethe fabrication of vertically extending side walls.

Returning to FIG. 3A, where droplet ejection is used to deposit polymerlayers, the controller 242 is communicatively coupled to the dropletejection printer 240 and controls aspects of the deposition process. Forexample, the controller 242 can control the size of the features thatare deposited by droplet ejection printer 240, e.g., by controlling thesize or number of droplets 242 ejected, the placement of the featuresthat are deposited, i.e., the x, y, or z-locations of the features,e.g., by controlling the timing of the ejection of the droplets as theprinthead scans across the workpiece, or the type of material that isdeposited by the controller, e.g., by controlling which printheadperforms ejection.

As shown in FIG. 3B, the first conformal coating 216 is deposited overthe first polymer layer 214 and exposed portions of the initialconformal coating (or exposed portions of the capping layer 117 orfront-plane 110, e.g., a light enhancement layer or other layer of thelight-emitting elements of the front-plane. The combination of the firstpolymer layer 214 and the first conformal coating 216 provides the firstdyad 110.

FIG. 3C illustrates a cross-sectional view of the front-plane 110 andthe first encapsulation sublayer 210, with the addition of a secondpolymer layer 224. The second polymer layer 224 includes polymer dots224 a that are deposited on top of the conformal coating 216.

Each polymer dot 224 a of the second polymer layer 224 can have an upperportion which has a convex top surface, e.g., each polymer dot 224 a canhave a substantially hemispherical top portion. In the implementationillustrated in FIG. 3C, each polymer dot 224 a can also include a bottomportion that fills a gap between the polymer dots 214 a of theunderlying dyad 210. However, as described below, other configurationsare possible. The convex top surface of the polymer dot 224 a of thesecond polymer layer 224 can project above the top surface of theconformal coating 216. The second polymer layer 224 can be deposited bydroplet ejection or a NIL/MIL process.

As shown in FIG. 3D, a second conformal coating 226 is deposited overthe second polymer layer 224. The combination of the second polymerlayer 224 and the first conformal coating 226 provides a second dyad220. Similar to the first encapsulation sublayer 210, the secondencapsulation sublayer 220 is formed by depositing a second polymerlayer 222 on top of the first conformal coating 212, followed by thedeposition of the second conformal coating 224 on top of the secondpolymer layer 222. Although FIG. 3D illustrates two layers of polymerdots, in some embodiments, additional layers of polymer dots can bedeposited. For example, an additional polymer layer can be deposited ontop of the second conformal coating 224 and an additional conformalcoating can be deposited on top of the additional polymer layer. In someembodiments, such an additional polymer layer and additional conformalcoating may be needed to fully cover the substrate.

In some implementations, an additional polymer layer 250 covers theoutermost conformal coating. The additional polymer layer 250 can bethicker than the polymer layers and/or conformal coatings of theencapsulation sublayers. In some implementations, the additional polymerlayer 250 can be deposited conformally, while in other implementationsthe additional polymer layer 250 can be deposited non-conformally, e.g.,such that the additional polymer layer has a substantially flat outersurface. The functional elements 111 can be formed on the additionalpolymer layer. The polymer dots of any one of the first or secondpolymer layers 214 or 224 are separated by respective conformalcoatings. A portion of the conformal coating 216 contacts a portion ofthe initial conformal coating 212 of the below first encapsulationsublayer 210. Similarly, a portion of the second conformal coating 226of the second encapsulation sublayer 220 contacts a portion of the firstconformal coating 216.

The portions of the conformal coatings 216 and 226 that contact theconformal coatings 212 and 216, respectively, can be referred to as“horizontal” portions of the conformal coatings because they extend overthe top surface of the immediately underlying conformal coating that isgenerally horizontal. Conformal coatings 216 and 226 includehorizontally portions 216 a and 226 a, respectively. The portions 216 b,226 b of the conformal coatings 216, 226 that are not in contact with aportion of another conformal coating can be referred to as “verticallyextending” portions of the conformal coating because they extend alongside walls of the underlying polymer dots and extend partially orentirely vertically. In general, the vertically extending portions canform an angle of at least 45° relative to the top surface of thefront-plane 110.

The conformal coatings 216, 226, also form side walls along sides of thepolymer dots 214 a and 224 a, respectively. The conformal coatings 216and 226 form the side walls 216 b and 226 b, respectively, which areemphasized by shading. The side walls 216 b and 222 b define wells inspaces between the side walls. The polymer layer 224 can completely fillthe wells defined by side walls 222 b.

In some embodiments, one or more additional layers can be added to fillthe wells defined by side walls 226 b. For example, an additionalpolymer layer can be deposited on top of the conformal coating 226 andan additional conformal coating can be deposited on top of theadditional polymer layer. The additional polymer layer can form asurface that is approximately coplanar with the xy-plane. That is, theadditional polymer layer can be a planarizing surface. The additionalconformal coating can be a dielectric layer that can perform permeationblocking for the underlying polymer and conformal coating layers.

In some implementations, the wells defined by the side walls 216 b areonly partially filled by the polymer layer 224. In some implementations,the side walls 226 b are only partially filled by any additional polymerlayers that are deposited on the conformal coating 226.

An encapsulation sublayer can also be referred to as a dyad. That is, adyad can include a polymer layer and an inorganic dielectric layer. TheOLED device illustrated in FIG. 3D includes an initial conformal coatingand two full dyads, i.e., the first and second encapsulation sublayers210 and 220. Therefore, the OLED device illustrated in FIG. 3D can bereferred to as a “2.5 dyad” device. The OLED device illustrated in FIG.2A can be referred to as a “2 dyad” device, and the OLED deviceillustrated in FIG. 2B can be referred to as a “1.5 dyad” device. Havinga conformal coating as the final layer deposited in the encapsulation102 provides certain advantages, e.g., ensuring that the polymerfeatures of the encapsulation remain where they were deposited.Therefore, while dyad devices higher than 2.5 are also possible.

FIG. 5A illustrates a top view of an encapsulation that includes thefirst and second polymer layers 214 and 224 with the polymer dots 214 a,214 b in a hexagonal close-packed structure. Polymer dots 214 a and 224a of the polymer layers 214 and 224 are included to show the positionsof the polymer dots of each polymer layer, relative to the polymer dotsof the adjacent layer. The polymer dots of the second polymer layer 224can be positioned over spaces between the polymer dots in the firstpolymer layer 214. Conformal coatings 222 and 232 are omitted from FIG.5A to better show the first and second polymer layers 214 and 224.

FIG. 5A shows a distance d₁, which is the diameter of each dot. Thediameter d₁, can be approximately 120 μm or less (e.g., 115 μm or less,110 μm or less, 105 μm or less, 100 μm or less). The diameter d₁ can bechosen according to the dimensions of the pixels of the OLED display.For example, when a pixel's footprint (lateral dimension) is viewed inthe xy-plane, can be chosen such that the footprint of the dot in thexy-plane approximately corresponds to the pixel's footprint. The pitchbetween the polymer dots can be about the same as the pitch between thepixels. The edges of the polymer dots can be aligned with gaps betweensubpixels, although this is not required.

FIG. 5A also shows a distance D_(x1), measured in the x-direction, whichis the distance between edges of neighboring polymer dots of either thefirst or second polymer layers 214 and 224, as measured along a linethat passes through the centers of the neighboring polymer dots. Thedistance D_(x1) can be approximately 90 μm or less (e.g., 80 μm or less,70 μm or less, 60 μm or less). In some implementations, the distanceD_(x1) can be less than d₁(2 cos(30)−1), e.g., approximately 0.73d₁ orless.

FIG. 5A also shows a distance D_(d1), measured diagonally, between thecenters of neighboring polymer dots of either the first or secondpolymer layers 214 and 224. The distance D_(d1) can be approximately 210μm or less (e.g., 190 μm or less, 170 μm or less, 150 μm or less, 130 μmor less, 110 μm or less, 90 μm or less, 70 μm or less, 50 μm or less).In some implementations, the distance D_(d1) can be approximately 2d₁cos(30), e.g., approximately 1.73d₁.

In some implementations, a third polymer layer can be deposited on topof the second polymer layer 224. For example, just like theconfiguration of the first and second polymer layers 214 and 224, thethird polymer layer can form the same hexagonally-packed configuration.As a result of the configuration of the polymer dots of the first andsecond polymer layers 214 and 224, and the polymer dots of the thirdpolymer layer, each of the empty spaces between three polymer dots ofthe first polymer layer 214 have a corresponding polymer dot of thethird polymer layer positioned above the empty space. That is, whenviewed from above, as in the planar view of FIG. 5A, when each polymerdot is deposited, no empty spaces can be seen between the polymer dotsof the first polymer layer 214. Accordingly, when each polymer dot ofthe third polymer layer is deposited, most or all of the conformal layer212 is obscured or encapsulated by the three polymer layers.

In some implementations, instead of being configured in a hexagonalconfiguration, as shown in FIG. 5A, the polymer dots of the polymerlayers are configured in a rectangular configuration, e.g., aconfiguration having orthogonal rows and columns of polymer dots. FIG.5B illustrates a top view of an example rectangularly-packedencapsulation, which includes the conformal coating 212, a first polymerlayer 514, and a second polymer layer 524. Polymer dots 514 a and 524 aof the polymer layers 514 and 524 are included to show the positions ofthe polymer dots of each polymer layer, relative to the polymer dots ofthe adjacent layer. The polymer dots of the second polymer layer 524 arepositioned over spaces between the polymer dots in the first polymerlayer 514. A separate conformal coating covers each of the first andsecond polymer layers 514 and 524, although the conformal coatings areomitted from FIG. 5B to better show the first and second polymer layers514 and 524.

FIG. 5B shows a distance d₂, which is the diameter of each dot. Thediameter d₂, can be approximately the same as the diameter d₁. Like d₁,d₂ can be chosen according to the dimensions of the pixels of the OLEDdisplay.

FIG. 5B also shows a distance D_(x2), measured in the x-direction, whichis the distance between edges of neighboring polymer dots of either thefirst or second polymer layers 514 and 524, as measured along a linethat passes through the centers of the neighboring polymer dots. Thedistance D_(x2) can be approximately 50 μm or less (e.g., 40 μm or less,30 μm or less). In some implementations, the distance D_(x2) can be lessthan d₂(√{square root over (2)}−1), e.g., approximately 0.4d₂ or less.

FIG. 5B also shows a distance D_(d2), which is the distance between thecenters of polymer dots of the same polymer layer and in the same row orcolumn. The distance D_(d2) can be approximately 170 μm or less (e.g.,160 μm or less, 150 μm or less, 140 μm or less, 130 μm or less). In someimplementations, the distance D_(d2) can be less than d₂√{square rootover (2)}, e.g., approximately 1.4d₂ or less.

While the polymer dots of the same polymer layer 214, 224, 514, or 524as shown in FIGS. 5A and 5B do not touch one another, in someimplementations, polymer dots of the same polymer layer can touch oneanother. For example, when polymer dots are arranged in a hexagonal,touching configuration, a single polymer dot can touches up to six dotsof the same polymer layer. In some implementations, the polymer dots ofthe same polymer layer are arranged in a rectangular, touchingconfiguration. When polymer dots are attached in a rectangular, touchingconfiguration, a single polymer dot touches up to four polymer dots ofthe same polymer layer. An advantage of discrete dots that are separatedon all sides is that the conformal dielectric coating extends verticallyalong the entire height of the polymer dot, increasing the length of theside wall and increasing the flexibility of the encapsulation.

When the OLED display 100′ is deformed, e.g., bent in the z-direction orstretched in the x and/or y-directions, the front-plane 110, functionalelements 111, substrate 112, back-plane 113, and the encapsulation 102are also deformed. In particular, when the OLED display 100′ isdeformed, the vertical portions 216 b and 226 b of the conformalcoatings 216 and 226 can splay outward, e.g., in the x and/ory-directions, while the polymer dots 214 a, 224 a are compressed andsquished outward. This can permit the inorganic material of theconformal coating to stretch or flex without significant risk of damage,while the total length of the conformal coatings remains roughlyconstant.

In addition, when the encapsulation 102 is deformed, the distancebetween the polymer dots can increase. When the distance between eachpolymer dot increases, the positions in the z-directions of the polymerdots of the second polymer layer 224 may change. However, because theconformal coating 212 coats the front-plane 110, the front-plane is notexposed when the OLED device 100A is bent or stretched.

When the OLED display 100′ is bent in the z-direction, the substrate112, the front-plane 110, and the encapsulation 102 is also deformed.The change in distance between polymer dots can increase, similarly tothe change in distance described above. The deformation of theencapsulation sublayers 210 and 220 are such that a polymer dot of thepolymer layer 224 remains above the empty space between any threepolymer dots of the polymer layer 214.

Despite the reduced risk of damage, sufficiently intense or repetitivestretching or bending may cause fractures in one or more of theconformal coatings 212, 216, and 226. The areas of the conformalcoatings that are most susceptible to fractures may be the verticalportions 216 b, 226 b, because of how the vertical portions arestretched or bent when the OLED display 100′ is stretched or bent. Whilesuch a fracture may be rare, the conformal coating 212 may fracture atthe vertical portions 216 b, 226 b. However, the structure of theencapsulation 102 ensures that an additional conformal coating ispresent between the facture and the front-plane. Moreover, even ifmultiple fractures occur, the staggered configuration of the polymerdots provides an increased path length to the front-plane.

FIGS. 6A-6C illustrate another example encapsulation method andstructure that can be used to protect the front-plane 110. Anotherexample encapsulation can be formed by depositing a pattern of polymersub-units on top of the front-plane 110 to form a first patternedpolymer layer. Following the patterned polymer layer, a conformalcoating can be deposited, the patterned polymer layer and conformalcoating together forming a first encapsulation sublayer. A secondencapsulation sublayer can be formed by depositing a second patternedpolymer layer on top of the first conformal coating, followed bydepositing a second conformal coating on top of the first patternedpolymer layer. A third encapsulation sublayer that includes a thirdpatterned polymer layer and a third conformal coating can be depositedon top of top of the second encapsulation sublayer. The first patternedpolymer layer can planarize the surface of the front-plane 110. Thesubsequent patterned polymer layers, e.g., the second and thirdpatterned polymer layers can also serve as planarization layers prior tothe deposition of additional layers, e.g., conformal layers orfunctional elements.

FIG. 6A illustrates a perspective view of a polymer subunit 602 that canbe deposited on top of the front-plane 110. The polymer subunit 602 canbe annular, i.e., has an aperture therethrough. The width of the annuluscan be generally uniform.

In the example of FIG. 6A, the polymer subunit 602 is athree-dimensional subunit having a substantially hexagonal shape whenviewed from above, i.e., when the viewing direction is along the z-axis.The polymer subunit 602 forms an annular shape with the six-sides ofhexagonal subunit forming six sidewalls. However, other annular shapesare possible, e.g., circular rings, square or rectangular annulus, etc.The polymer subunit 602 can be formed from the same material ormaterials that form the polymer dots of FIGS. 3A-3D. In addition, thepolymer subunit 602 can be deposited by similar process, e.g., MIL/NIL.

While FIG. 6A illustrates a single polymer subunit 602, FIG. 6Billustrates the polymer subunit coated by a conformal coating 610 toform an encapsulation cell 612. The conformal coating 610 can be formedfrom the same material or materials that form the conformal coatings ofFIGS. 3A-3D, e.g., a dielectric material. In addition, the conformalcoating 610 can be deposited by similar process, e.g., a vapordeposition process. The conformal coating 610 forms a bottom surfacelayer 614 extending in the x and y-directions and having a hexagonalshape when viewed from above. Accordingly, the encapsulation cell 612forms a cup that includes side walls and the bottom surface layer 614.

While FIG. 6B illustrates a perspective view of a single encapsulationcell 612, FIG. 6C illustrates a perspective view of multipleencapsulation cells positioned next to one another to form a firstencapsulation sublayer 620. The first encapsulation sublayer 620 is alattice of encapsulation cells that together form a structure that issimilar in shape to a honeycomb. While omitted from FIG. 6C to bettershow the honeycomb lattice, the first encapsulation sublayer furtherincludes a planarizing polymer layer disposed over the lattice ofencapsulation cells.

Whereas FIG. 6A illustrates a perspective view of a single cell for anencapsulation sublayer 620, FIG. 7A illustrates a cross-sectional viewof the first encapsulation sublayer which includes two adjacentencapsulation cells 612, 712. FIG. 7A further includes the front-plane110 with an initial conformal coating 704 deposited over thefront-plane, e.g., deposited over the capping layer 117 of the cappinglayer. The conformal coating 704 can be an inorganic dielectric layer,e.g., as described for initial conformal coating 212.

Each encapsulation cell 612 and 712 includes a polymer subunit, aportion of a conformal coating, and a planarizing polymer layer. Forexample, referring to encapsulation cell 612, FIG. 7A includes thepolymer subunit 602, the conformal coating 610, and a planarizingpolymer layer 702 a. Because polymer layer 702 a is a planarizing layer,it may be thicker, as measured in the z-direction, than subsequentlydeposited polymer layers. The planarizing polymer layer 702 a can fillthe inner recess that is surrounded by the annular polymer subunit 602,as well as fill the spaces between adjacent polymer subunits 602. Thisfacilitate the deposition of additional encapsulation sublayers. Inaddition, an optional planarizing separating polymer layer 702 b can bedisposed over the conformal coating 610 and a planarizing polymer layer702 a. This provides separation between the conformal coatings ofdifferent encapsulation layers.

Both encapsulation cell 612 and encapsulation cell 614 are emphasized byheavy dashed lines. Each encapsulation cell has a diameter, measured inthe x-direction, which is labeled C_(d) in FIG. 7A. Each encapsulationcell also has a height, measured in the z-direction, which is labeledC_(h) in FIG. 7A. The gap between each encapsulation cell is labeledC_(g).

The dimensions, e.g., the diameter, height, and cell gap with respect toencapsulation cells of the first, second, or third encapsulationsublayers can be approximately the same. The diameter, C_(d), isapproximately 1000 μm or less (e.g., 980 μm or less, 960 μm or less, 940μm or less, 920 μm or less, 900 μm or less). The height, C_(h), isapproximately 5 μm or less (e.g., 4.75 μm or less, 4.5 μm or less, 4.25μm or less, 4 μm or less, 3.75 μm or less). The gap between neighboringencapsulation cells, C_(g), is approximately 90 μm or less (e.g., 85 μmor less, 80 μm or less, 75 μm or less, 70 μm or less). The dimensions ofthe encapsulation cells may change depending on the pixel density.

The diameter C_(d) can be chosen according to the dimensions of thepixels of the OLED display. In some implementations, when a pixel'sfootprint is viewed in the xy-plane, C_(d) can be chosen such that thefootprint of the encapsulation cell in the xy-plane approximatelycorresponds to the pixel's footprint. That is, C_(d) can beapproximately equal to the x or y dimension of the pixel. In otherimplementations, C_(d) is an integer multiple of the x or y dimension ofthe pixel.

While the first encapsulation sublayer 620 can be used to encapsulatethe front-plane 110, including additional encapsulation sublayers in anencapsulation results in increased protection and durability. FIG. 7Billustrates a cross-sectional view of the front-plane 110, substrate112, and three encapsulation sublayers in an aligned configuration. FIG.7B illustrates the encapsulation sublayer 620 and a third and secondencapsulation sublayer 720 a and 720 b, each emphasized by dotted lines.The encapsulation sublayer 620 includes the encapsulation cell 612, andthe encapsulation sublayers 720 a and 720 b include encapsulation cells712 a and 712 b, respectively. Each encapsulation cell 612, 712 a, and712 b is emphasized by heavy dashed lines. The encapsulation sublayersof FIG. 7B are said to be aligned because each encapsulation cell isaligned either directly above, directly below, or both directly aboveand directly below another encapsulation cell of a differentencapsulation sublayer. For example, an encapsulation cell 712 b of thesecond encapsulation sublayer 720 b is aligned directly above theencapsulation cell 612 of the first encapsulation sublayer 620, andaligned directly below an encapsulation cell 712 a of the thirdencapsulation sublayer 720 a.

While FIG. 7B illustrates a cross-sectional view of an encapsulation700B that includes the three cells of the encapsulation sublayers 620,720 a, and 720 b, in an aligned configuration, FIG. 7C illustrates across-sectional view of an encapsulation 700C in which the cells of thethree encapsulation sublayers 620, 720 a, and 720 b are in an unalignedconfiguration. In particular, FIG. 7C illustrates the cells of the threeencapsulation sublayers 620, 720 a, and 720 b in a staggeredconfiguration. Instead of each encapsulation cell being aligned directlyabove, directly below, or both directly above and directly below anotherencapsulation cell, as in FIG. 7B, only some encapsulation cells arealigned above or aligned below another encapsulation cell. For example,the encapsulation cell 612 is aligned below the encapsulation cell 712a, but not directly below, because the encapsulation cell 712 bseparates the encapsulation cells 612 and 712 a.

In the example of FIG. 7C, although the three encapsulation structures620, 720 a, and 720 b are in an unaligned configuration, theencapsulation cells of the first and third encapsulation sublayers 620and 720 a are approximately aligned. In other implementations, when anencapsulation is formed by encapsulation sublayers 620, 720 a, and 720b, the encapsulation sublayers are in a completely unalignedconfiguration. When the encapsulation sublayers are completelyunaligned, none of the encapsulation cells of the encapsulationsublayers 620, 720 a, and 720 b are aligned.

In the example of FIG. 7C, the gaps between neighboring encapsulationcells of the second encapsulation sublayer 720 b are approximatelyaligned with the centers of encapsulation cells of the first and thirdencapsulation sublayers 620 and 720 a although in other implementations,the gaps between neighboring encapsulation cells of second encapsulationsublayer 720 b are not aligned with the centers of encapsulation cellsof the first and third encapsulation sublayers 620 and 720 a.

FIG. 8 illustrates a possible configuration for hexagonal cells of anencapsulation sublayer. The cross-sectional direction A-A′ approximatelycorresponds to the cross-sectional direction illustrated in FIGS. 7A-7B.

One advantage of an unaligned configuration (e.g., as shown in FIG. 7C)over an aligned configuration (e.g., as shown in FIG. 7B) is that theformer can be easier and/or faster to manufacture than the latterbecause the machinery used to deposit the third and second encapsulationsublayers 720 a and 720 b need not account for aligning the layers tothe first encapsulation sublayer 620.

Returning to FIGS. 2A and 2B, in some implementations the encapsulationis aligned relative to the pixels or subpixels of the front-plane. Inparticular, the side walls of the polymer islands 214 a in one or moreof the polymer layers can be positioned vertically over the gap betweenadjacent subpixels. Similarly, the vertically extending portions 216 aof conformal layer 216 can also be positioned vertically over the gapbetween adjacent subpixels. For example, the side walls of the polymerislands 214 a and the vertically extending portions 216 a can bepositioned over the plateau of the PDL 115 (see FIG. 2A), or over thegap between anodes 114 a of adjacent OLED devices (see FIG. 2B). Thisconfiguration reduces the likelihood of unwanted reflections, thusincreasing transmittance and reducing the likelihood of visual defects.

In some implementations, the dimensions of the encapsulation 102 cancorrelate with the pixel geometry of the front-plane 110. For example,the pitch of the cells of the encapsulation 102 can be an integermultiple of the pitch of the subpixels. Although FIGS. 2A and 2Billustrate systems in which the pitch of the cells 130 of theencapsulation 102 are equal to the pitch of the subpixels, this is notrequired.

Example RGB pixel geometries of the front-plane 110 include triangular,diagonal, stripe, and PenTile. FIG. 9A illustrates a stripe pixelgeometry 800A, while FIG. 9B illustrates a schematic cross-sectionalview of a portion of the stripe pixel geometry.

Referring to FIG. 9A, the stripe pixel geometry 800A includes columns804 a of red subpixels 804, columns 806 a of green subpixels 806, andcolumns 808 a of blue subpixels 808. An example pixel 802 includes onesub-pixel of each color, e.g., sequential sub-pixels along a row.However, other configurations are possible, e.g., a pixel could includefour of each color subpixel. FIG. 9B further illustrates a space 908between adjacent subpixels.

The cells 830 of one or more encapsulation sublayers can span multiplesubpixels. For example, each cell 830 can span a number of subpixelscorresponding to an integer, n, multiple of the number of subpixels in apixel, e.g., while the cell 830 includes one subpixel of each color, alarger cell can include an integer multiple of each subpixel. Forexample, FIG. 9A includes a cell 840 that includes four subpixels ofeach color, making the integer multiple n=4.

In some implementations, e.g., as shown in FIGS. 9A and 9B, the edges ofthe cells 830 in one or more encapsulation sublayers are aligned withthe edges of the pixels. For example, the edges of the cells, i.e., thevertically extending portions 216 a of the conformal layer 116, can bealigned with the spaces between adjacent subpixels (regardless ofwhether the cells are aligned with the pixels or span subpixels fromdifferent pixels). However, the cells 830 can be offset relative to thepixels.

When an OLED display, such as the OLED display 100A′, includes the pixelgeometry 800A, the dimensions of the polymer features of theencapsulation 102 can vary depending on the pixel density and pixelsize. For example, for an encapsulation that includes pixels 802 for adisplay having a pixel density of 200 ppi, the diameter, C_(d), of anencapsulation cell can be about 120 μm to about 135 μm (e.g., about 124μm to about 130 μm). If instead an encapsulation includes cells that arean integer multiple of the cell 803 at a pixel density of 200 ppi,C_(d), can be integer multiples of the aforementioned ranges, e.g.,about 240 μm to about 270 μm. For pixel densities of 200 ppi, theencapsulation cells can have a height of a 1 μm to about 20 μm.

As another example, for an encapsulation that includes cells 840 thatspan multiple subpixels of the same color, for a display having a pixeldensity of 400 ppi, the diameter, C_(d), of an encapsulation cell (e.g.,the encapsulation cell 612) can be about 60 μm to about 70 μm (e.g.,about 60 μm to about 65 μm). If instead an encapsulation includes cellsthat are an integer multiple of the cell 840 at a pixel density of 400ppi, C_(d), can be integer multiples of the aforementioned ranges. Forexample, while cell 840 has four times as many subpixels of a certaincolor compared to the number of subpixels of the same color of cell 830,C_(d) for an encapsulation that includes cells 840 can be double theC_(d) for an encapsulation that includes cells 830. For pixel densitiesof 400 ppi, each example pixel 802 and can include encapsulation cellshaving a height, C_(h), of about 1 μm to about 10 μm.

The spacing, as measured in the x or y-directions, between adjacentpixels can vary depending on the aperture ratio of the OLED device. Forexample, for aperture ratios of 70% the distance between adjacent pixelscan be about 8 μm to about 14 μm, while for aperture ratios of 90% thedistance between adjacent pixels can be about 2 μm to about 5 μm.

Referring now to FIG. 10, the PenTile pixel geometry 800B includescolumns of green subpixels 822 a and rows of green subpixels 822 b. ThePenTile pixel geometry 800B also includes columns of alternating red andblue subpixels 824 a and rows of alternating red and blue subpixels 824b. The PenTile pixel geometry further includes two example pixel sizes828 and 830, each of which is outlined by a solid line.

In some implementations, the side walls of the polymer islands 214 a andthe vertically extending portions 216 a of conformal layer 216 arepositioned in about the same location for each pixel, e.g., verticallyover about the center of the pixel. In some implementations, d₁ and d₂are chosen such that the vertically extending portions of conformallayers approximately align with the spaces between pixels. In someimplementations, C_(d) is chosen such that the side walls of anencapsulation cell approximately align with the spaces between pixels.

Pixel 828 includes four halves of four different green subpixels, fourquarters of four different red subpixels, and one blue subpixel. In someimplementations, instead of including four red quarters and a bluesubpixel in the middle of the pixel, a pixel of the same size as pixel828 can include four green halves, four blue quarters, and a redsubpixel in the middle of the pixel. Pixel 830 includes four greensubpixels, two red subpixels and two blue subpixels. The pixel densityof the PenTile pixel geometry 800B can be approximately 575 ppi. Thedimensions of the dielectric component of an encapsulation used toencapsulate an OLED display that includes the PenTile pixel geometry800B, e.g., the encapsulation 102, can vary depending on the pixel size.

For example, while the encapsulation cell is not illustrated in FIG. 10for an encapsulation that includes pixels 828, the diameter, C_(d), ofan encapsulation cell can be about 75 μm to about 85 μm, while for thepixel size 830, the diameter, C_(d), of the encapsulation cell can beabout 105 μm to about 125 μm. For both pixels 828 and 830, and caninclude encapsulation cells can have a height, C_(h), of a 1 μm to about20 μm.

In some implementations, an expanded pixel spans more subpixels than arespanned by the pixels 1002 or 1004. In such implementations, the edgesof a cell can be aligned with the edges of the subpixels spanned by theexpanded pixel.

Although the description above focuses on organic light-emitting diodes,the techniques can be applicable to light-emitting diodes formed frominorganic materials, or to electronic displays that include other typesof light-emitting components, such as quantum dots, or light-blockingcomponents, such as liquid crystal displays. In addition, theencapsulation can be applicable to other flex/stretchable electronicsthat need protection from ambient oxidants.

Rather than having a hemispherical upper portion, the polymer dots canhave other shapes, such as a trapezoidal cross-section. The conformalcoating would then form sloped side walls along the inclined outersurface of the trapezoidal polymer dots.

In addition to disclosing TFEs that are stretchable and flexible, theTFEs of this disclosure can be further equipped with additionalfunctions by appropriately selecting the materials and architectures ofthe TFEs. For example, the one or more materials that make up thepolymer layers can be chosen so that the layers have an index ofrefraction that is close to or greater than the index of refraction ofthe organic materials of the OLED stack, which can be approximately 1.8or larger. In such a case, the total internal reflection angle for theemitted light as it exits the OLED stack and enters the TFE layers wouldbe increased, thereby enhancing the light outcoupling into the TFE. Thelight outcoupling into the TFE can be enhanced by allowing lightgenerated by the OLEDs to be emitted in more divergent angles such thatthey are not reflected but outcoupled. Example polymer materials includecolloidal dispersions of high index nanoparticles of high index oxides,like TiO₂ and ZrO₂. Such materials can raise the effective index ofrefraction of polymer materials.

The disclosed dielectric layers can also reduce the divergence of lightemitted from OLEDs, which is typically near Lambertian dispersion. Byplacing multiple NIL or MIL produced features of dielectrics within apixel area, and by tailoring the curvature of the top surface of thepolymer in the pixel area, as illustrated in FIGS. 6B and 6C, refocusingof the light emitted at higher angles can be achieved. Such lowerdivergent input light source can be used to enable controlled deflectionof the light to create the so-called light-field based 3D display, wherea “pixel” in a light-field 3D display comprises multiple regular pixels,each of which renders a given image in multiple directions to create 3Dimagery.

1-20. (canceled)
 21. A method of encapsulating an organic light-emittingdiode display, the method comprising: ejecting droplets of a firstliquid polymer precursor onto a light-emitting side of a display layerhaving an array of light-emitting diodes; curing the first liquidpolymer precursor to form a plurality of first polymer projections thathave spaces therebetween that expose an underlying surface with both theplurality of first polymer projections and spaces therebetweenpositioned over the array of light-emitting diodes; and conformallycoating the first polymer projections and the spaces between the firstpolymer projections with a first dielectric layer such that the firstdielectric layer has side walls along sides of the first polymerprojections and defines wells in spaces between the side walls.
 22. Themethod of claim 21, further comprising depositing a first polymer fillerto at least partially fill the wells between the side walls.
 23. Themethod of claim 22, wherein the first polymer filler fills the wells andcovers the first dielectric layer in regions over the first polymerprojections.
 24. The method of claim 21, comprising depositing anunderlying dielectric layer to contact and conformally covering thedisplay layer, and depositing the first polymer projections on theunderlying dielectric layer.
 25. The method of claim 24, wherein theunderlying dielectric layer is the same material as the first dielectriclayer.
 26. The method of claim 21, comprising ejecting droplets ofliquid polymer precursor directly on the display layer.
 27. The methodof claim 26, comprising ejecting droplets of liquid polymer precursordirectly on a capping layer of the display layer.
 28. The method ofclaim 21, wherein ejecting droplets of liquid polymer precursorcomprises ejecting a sequence of droplets with each droplet forming asingle projection from the plurality of first polymer projections. 29.The method of claim 28, wherein the droplet forms a curved convexprojection on the underlying surface.
 30. The method of claim 21,comprising: ejecting droplets of a second liquid polymer precursor ontothe first dielectric layer; curing the second liquid polymer precursorto form a plurality of second polymer projections that have spacestherebetween that expose an underlying surface with both the pluralityof second polymer projections and spaces therebetween positioned overthe array of light-emitting diodes; and conformally coating the secondpolymer projections and the spaces between the second polymerprojections with a second dielectric layer such that the seconddielectric layer has side walls along sides of the second polymerprojections and defines wells in spaces between the side walls.
 31. Themethod of claim 30, wherein the plurality of first polymer projectionsand the plurality of second polymer projections are the same polymermaterial, and the first dielectric layer and second dielectric layer arethe same dielectric material.
 32. The method of claim 30, wherein thesecond dielectric layer contacts first dielectric layer.
 33. The methodof claim 21, wherein the spaces between the side walls and the sidewalls are aligned with gaps between the light emitting diodes.
 34. Amethod of encapsulating an organic light-emitting diode display, themethod comprising: performing imprint lithography to deposit a pluralityof first polymer projections that have spaces therebetween that exposean underlying surface with both the plurality of first polymerprojections and spaces therebetween positioned over the array oflight-emitting diodes of a display layer; and conformally coating thefirst polymer projections and the spaces between the first polymerprojections with a first dielectric layer such that the first dielectriclayer has side walls along sides of the first polymer projections anddefines wells in spaces between the side walls.
 35. The method of claim34, wherein the imprint lithography comprises micro-imprint ornano-imprint lithography.
 36. The method of claim 34, wherein theplurality of first polymer projections have a flat top surface.